Make backreference support clear.

Fixes #268.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/app.rs b/src/app.rs
index fe80a069..13b1ac60 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -5,6 +5,10 @@ use clap::{App, AppSettings, Arg, ArgSettings};
 const ABOUT: &'static str = "
 ripgrep (rg) recursively searches your current directory for a regex pattern.
 
+ripgrep's regex engine uses finite automata and guarantees linear time
+searching. Because of this, features like backreferences and arbitrary
+lookaround are not supported.
+
 Project home page: https://github.com/BurntSushi/ripgrep
 
 Use -h for short descriptions and --help for more details.";